Entourage file attachment limitations are managed by the Exchange 2007 server in the EWS folder.
There's no easy-to-use checkbox to say someone has no limitation on attachment file size.
Assuming that when you don't impose an attachment size limitation on a user-- presumably because you don't want there to be a limitation on their attachment sizes-- is enough won't work. Exchange applies its default limitation of 5mb!
When setting a higher limit to allow someone to send attachments larger than 5mb, don't base the new limit on the actual size of the attachment files. Mime will expand attachments about 1/3 larger than their original file size. But don't base the new limit on that size either, because Exchange expands the attachments even larger! Set the limit to about double the original attachments' file size.
Many Mac users work on media files. While email isn't the best way to send large files, some will want to quickly send large (25-50mb) attachments. Microsoft will be wise to simplify this process.
Here’s the technical instructions…..
In addition to running the appropriate cmdlets to change message size limits in Exchange, you'll need to edit web.config found in C:\Program Files\Microsoft\Exchange Server\ClientAccess\exchweb\ews. Open with Notepad (or your favorite text editor) and search for maxrequestlength. Change the value to reflect the size in kilobytes desired, then save the change.
For good measure, edit web.config located in C:\Program Files\Microsoft\Exchange Server\ClientAccess\owa.
Once both files have been edited open a command prompt and run the following commands:
appcmd set config "Default Web Site/ews" -section:requestFiltering -requestLimits.maxAllowedContentLength:[size in Bytes!]
appcmd set config "Default Web Site/owa" -section:requestFiltering -requestLimits.maxAllowedContentLength:[size in Bytes!]
Note: replace [size in Bytes!] with the actual number of bytes based on the settings you chose for the web.config files.
After IIS has restarted you should be able to send large attachments; just like a Staples Button - That was easy.